Juvenile hydrocephalus is a neurological disease that affects 1 in every 1000 human children. Hydrocephalus results from increased cerebral spinal fluid (CSF) in the ventricles of the brain, and may be due to overproduction of CSF, decreased removal, or a blockage to fluid flow. Left untreated, the increasing intracranial pressure causes neuronal cell loss and ultimately death. A significant percentage of hydrocephalus is believed to be genetic in nature, yet little is known about genetic causes of the disease. Animal model systems for hydrocephalus, which are genetically tractable, can prove valuable in identifying candidate genes and studying their functions. The transgenic mouse line Jh (juvenile hydrocephalus) carries an insertion of a lacZ reporter transgene, under the control of a minimal promoter, on mouse chromosome 9. Mice homozygous for the Jh insertion develop hydrocephalus by 1-2 weeks of age, and few survive beyond 8 weeks. Molecular characterization of the Jh integration has shown that the transgene disrupts an uncharacterized gene that will be called I11. The integration event deleted the I11 exon 5 splice acceptor site, and no protein is produced from the mutant allele. Preliminary evidence indicates that a transgene carrying the I11 gene can rescue the Jh phenotype. These data indicate that the I11 gene plays a role in CSF balance, and the gene is expressed in cell types that are involved in CSF regulation, including the choroid plexus and ventricular ependyma. The predicted I11 protein has no known functional domains, however, so its normal physiological role is still unknown. Characterization of the Jh mice, and functional investigation of the I11 protein, will provide valuable information about CSF regulation and the etiology of juvenile hydrocephalus. This proposal describes a preliminary genetic and physiological analysis of the Jh mice, and a characterization of the I11 protein. The results of these experiments will direct the experimental design for long-term study of these animals. Specifically, this proposal will 1) use electron microscopy and CSF protein characterization to identify any brain abnormalities associated with the Jh phenotype, 2) biochemically characterize the I11 protein to determine its post-translational processing and subcellular localization, and use morpholino knockdown of the zebrafish I11 ortholog to determine conservation of function across species, and 3) use immunohistochemistry and in situ hybridization to survey the expression of marker genes for key cell types involved in CSF regulation, assaying their proper differentiation and function. PUBLIC HEALTH RELEVANCE: Congenital hydrocephalus is one of the most common childhood neurological diseases, yet it is poorly understood and available treatments are only palliative. The Jh mouse line provides a tractable animal model system for studying the genetic causes and physiological mechanisms underlying juvenile hydrocephalus. A more thorough understanding of this disease is likely to lead to better treatment options for human children with hydrocephalus.